2. Field of the Invention
The present invention relates to a compressor valve used on compressors, and in particular to a compressor valve which includes a valve seat having flow channels therethrough, a catch positioned at a distance from the valve seat, and a spring-loaded plug which moves between the valve seat and the catch to control the flow of gaseous medium through the valve.
2. The Prior Art
As is well known, independently operating compressor valves on compressors for a gaseous medium are controlled by the flow of the gaseous medium therethrough, i.e., the spring-loaded plug is lifted off the valve seat to allow the gaseous medium to flow through the valve by the force of the flowing gaseous medium. On the other hand, the springs acting on the spring-loaded plug make sure that the plug will move to close the valve when a gaseous medium is not flowing therethrough (pressureless condition). They also dampen the impact of the plug against the lift stop when the plug is moved away from the valve seat and they initiate the timely movement of the plug back towards the valve seat (closing motion).
The force of the gaseous medium on the plug will be determined to a large extent on the rotational speed of the compressor and on the specific weight of the gaseous medium. With a constant cross section of flow channels through the valve, the flow rate of gaseous medium and the force acting on the plug will increase with increasing rotational speed of the compressor. The force of the gaseous medium on the plug will also increase with an increase in the specific weight of the gaseous medium. In order to achieve a proper operation of the compressor valve, the spring pressure acting on the plug has to be selected with regard to the force from the flowing gaseous medium, and thus the rotational speed of the compressor and the specific gas weight. In this regard, if the spring force is too low, given the rotational speed of the compressor and/or the specific weight of the gaseous medium, the opening motion of the plug will not be sufficiently dampened and the closing motion will be initiated too late, thus causing hard impacts on the lift stop and the valve seat. On the other hand, if the spring force is too high, the valve will open too late and the plug will flutter, i.e., because the current force of the gaseous medium will not be sufficient to keep the plug securely positioned against the lift stop. Of course, if the compressor is driven at a constant rotational speed and if the flowing gaseous medium has a constant specific weight, the required spring force can be calculated and provided for. However, if during operation the rotational speed of the compressor varies, or if during operation the specific weight of the flowing gaseous medium changes, special measures may be needed to adapt the valve to these changing operational conditions.
In Austrian Patent 317,403 a valve is disclosed which includes two plugs for controlling the flow through the flow channels in the valve seat, one being arranged above the other. The plug which sits directly on the valve seat has openings which are covered by the second plug thereabove. In addition, separate lift stops are provided for the two plugs, these two lift stops being located at different distances from the valve seat. The upper plug which covers the openings of the other plug is under a greater spring force than the lower plug which contacts the valve seat. When the valve is opened, both plugs are simultaneously lifted off the valve seat. When the compressor is operated at a high rotational speed, thus producing a high current force of the gaseous medium, both plugs are moved against their respective lift stops and are held there without fluttering. When the compressor is operated at a low rotational speed, the two plugs are simultaneously lifted to only the closer lift stop and do not become separated. As such, this valve provides only a limited adaptation to varying rotational speeds of the compressor.
It is an object of the present invention to provide a compressor valve which can adapt to varying operational conditions of the compressor to which it is connected, in particular to its rotational speed and the specific weight of the medium being transported therethrough.